Radon gas is a significant health hazard that has recently been recognized as causing up to 20,000 deaths each year in the United States alone. The United States Environmental Protection Agency has estimated that one million to five million homes may have unhealthful radon levels. In non-inhabited areas, radon gas naturally diffuses through the soil into the atmosphere where it is harmlessly dispersed. Wherever there is a house, however, the radon gas leaks into subterranean rooms around the foundation slab and through cracks in the foundation or subterranean walls, and diffuses through porous cement and concrete blocks. And, since radon is heavier than air, the subterranean room acts as a collector of radon gas, holding and concentrating the gas to lethal levels.
The Environmental Protection Agency has published A HOMEOWNER'S GUIDE, August, 1986, OPA-86-005, and TECHNICAL GUIDANCE Manuals, EPA/625/5-86/019 (1st edition) and EPA/625/5-87/019 (2d edition) that outline methods for reducing radon gas concentrations inside subterranean rooms of houses or other structures. While many of the methods for reducing radon gas concentrations described in these pamphlets includes the use of some type of discharge fan, in each case the discharge fan is mounted above the ground level or inside or attached to the house or enclosure.
The placement of a ventilation fan above ground or inside or attached to a house or enclosure may have harmful or distracting side-effects. First, an improperly mounted fan or a fan that is incompletely sealed to a discharge vent may allow re-entrainment of the unwanted noxious gas that the apparatus is designed to disperse. Second, if the fan is mounted outside the enclosure or in an uninsulated location, ice and moisture may build up in the piping network that would have the effect of reducing the suction of the fan. Third, depending on the location of the fan in relation to the piping network, moisture may condense or other debris may enter the fan assembly and cause corrosion or mechanical problems for the fan assembly itself. Finally, from a more cosmetic standpoint, a bulky fan assembly may be mounted in a place that is difficult to access and may be unattractive and very noisy. The EPA pamphlets neither offer solutions to these problems or even suggest the existence of these practical hazards.